KR100289059B1 - Novel luminescent polymer containing naphthalene and carbazole, preparation method thereof and electroluminescent device using same - Google Patents

Abstract

The present invention relates to a light emitting polymer, a method for manufacturing the same, and an electroluminescent device using the same, wherein the light emitting polymer according to the present invention includes a naphthalene vinylene unit and a carbazole vinylene unit, as represented by the following Formula 1 or Formula 2. It has a structure that repeats regularly. In addition, the method of manufacturing a light emitting polymer according to the present invention comprises the step of reacting the phosphonium salt or phosphonate salt of naphthalene with the carbazole dialdehyde or the Wittich-Emones reaction, the electroluminescent device according to the present invention The light emitting polymer is used in at least one layer of the light emitting layer and the hole transporting layer.

[Formula 1]

[Formula 2]

Description

Novel luminescent polymer containing naphthalene and carbazole, preparation method thereof and electroluminescent device using same

The present invention relates to a light emitting polymer, a method for manufacturing the same, and an electroluminescent device using the same, and a novel light emitting polymer including naphthalene and carbazole having excellent light emission efficiency and hole transporting ability, and a method for manufacturing the same, and the light emitting polymer It relates to an electroluminescent device used.

Electroluminescence is a phenomenon in which free electrons accelerated by an electric field emit light by exciting electrons present in a light emitting material and releasing energy when it is returned to the original state. It is widely used in devices and optical amplifiers.

FIG. 1 is a schematic cross-sectional configuration diagram of a general multi-layer thin film electroluminescent device. As shown in FIG. 1, a multilayer thin film electroluminescent device includes a substrate 1 such as a glass substrate and a transparent layer placed on the substrate 1. Or translucent electrode 2, light emitting layer 4, hole transport layer 3 for transporting holes to light emitting layer 4, electron transport layer 5 for transporting electrons to light emitting layer 4, and electron transport layer 5 ) And a metal electrode 6 made of Al or the like. At this time, in the multilayer thin film electroluminescent device, when the above-described hole transport layer 3 and the electron transport layer 5 are not formed, a single layer electroluminescent device is configured.

Conventionally, although the inorganic material was used for the above-mentioned light emitting layer 4, in recent years, a polymer is mainly used. As a light emitting material widely known as a light emitting material of such a polymer electroluminescent device, poly (1,4-phenylenevinylene) (PPV), polyparaphenylene (PPP), and polythiophene which are well known conductive polymers ? -Conjugated polymers such as (PT). Among them, PPV and its derivatives are most widely used as light emitting materials for electroluminescent devices. PPV is not only used as a light emitting layer 4 itself, but also has excellent hole transporting properties, so that it can be used as a hole transporting layer 3 in a multilayer thin film device. Also used a lot. The prior art using such a PPV or a derivative thereof as an electroluminescent device is disclosed in the following literatures.

U. S. Patent No. 5,247, 190, and J, H, Burroughes et al, “Light-emitting diodes based on conjugated polymers”, Nature, 347, 539, 1990, after forming PPV into a film in the water-soluble prepolymer state, A method of synthesizing conjugated π-conjugated polymer by heat-removing and removing at high temperature, and spin-coding PPV prepolymer on transparent indium tin oxide (ITO), followed by heat treatment to produce PPV, and a metal electrode such as Al The method for manufacturing an electroluminescent device by coating a film is described.

U.S. Patent No. 5,514,878 also discloses a poly (cyanoterephthalylidene) (poly (cyanoterephthalylidene): CN-PPV), which is a light emitting polymer containing a CN group having a high electron affinity, and a PPV as a hole transport layer. Disclosed is a method of manufacturing a two-layer thin film electroluminescent device using PPV as an electron injection layer.

Furthermore, in C. Zhang et al, “Improved efficiency in green polymer light-emitting diodes with air stable electrodes”, J. Electronic Materials, 23, 453, 1994, PBD, an oxydiazole derivative, using an electron transport layer, PPV A derivative of poly (2-cholestanoxy-5-texyldimethylsilyl-1,4-phenylenevinylene) [poly (2-cholestan-oxy-5-thexyldimethylsilyl-1,4-phenylenevinylene): CS-PPV] Using a light emitting layer, PBD is dispersed in CS-PPV which is a light emitter, and then coated on ITO which is a transparent electrode, and Al is deposited on a metal electrode to produce an electroluminescent device.

However, PPV and its derivatives used in the above-mentioned prior art are generally synthesized through a prepolymer soluble in water or an organic solvent in the manufacture of an electroluminescent device, and the final π-conjugated polymer form through a high temperature heat treatment process. Will be achieved. Such a high temperature heat treatment process in the electroluminescent device manufacturing process has a problem that the workability of the electroluminescent device is greatly reduced. In addition, the above-mentioned light emitting polymer PPV is not dissolved in an organic solvent, thereby degrading workability and workability, and also degrading hole transport characteristics and light emitting characteristics, and the electroluminescent device manufactured using the light emitting polymer is degraded under high voltage. It has the disadvantage of being easy.

As a result, the main object of the present invention is to provide a light emitting polymer having excellent light emission characteristics and hole transport characteristics, being soluble in an organic solvent, and having good processability and workability.

Still another object of the present invention is to provide a method of manufacturing the light emitting polymer according to the present invention, simply and economically.

In addition, another object of the present invention is to provide an electroluminescent device using the light emitting polymer that not only has excellent light emission characteristics and hole transport characteristics, but also stably operates without deterioration under high voltage.

1 is a schematic cross-sectional view of a general multilayer thin film electroluminescent device.

2 is a UV absorption spectrum of the light emitting polymer prepared by the preferred embodiment of the present invention.

3 is a PL emission spectrum of the light emitting polymer prepared by the preferred embodiment of the present invention.

4 is an EL emission spectrum of a single layer light emitting device using a polymer prepared according to a preferred embodiment of the present invention.

5 is a graph showing the current-voltage characteristics of a single layer light emitting device using a polymer prepared according to a preferred embodiment of the present invention.

6 is a graph showing the voltage-luminescence intensity characteristics of a single layer light emitting device using a polymer prepared according to a preferred embodiment of the present invention.

* Explanation of symbols for main parts of the drawings

1 substrate 2 translucent electrode

3: hole transport layer 4: polymer light emitting layer

5: electron transport layer 6: metal electrode

In order to achieve the above object of the present invention, the light emitting polymer according to the present invention, naphthalene vinylene and carbazole vinylene unit having a high luminous efficiency and excellent hole transport characteristics, as represented by the following formula (1) or (2) It has a structure that repeats regularly:

Wherein R = C1-C20 linear or branched alkyl group.

At this time, R = C1-C20 linear or branched alkyl group is represented, n> 4.

In addition, in order to achieve the above object of the present invention, the manufacturing method of the light emitting polymer according to the present invention represented by the formula (1), the phosphonium salt of naphthalene represented by the formula (3) or (Formula 4) A phosphonate of naphthalene is characterized by comprising the step of reacting the carbazole dialdehyde represented by the following formula (5): Wittig or Wittig-Emons reaction :

In this case, X = halogen, R = C1-C20 linear or branched alkyl group.

Moreover, in order to achieve the above object of the present invention, the method for producing a light emitting polymer according to the present invention represented by the formula (2) is a phosphonium salt of naphthalene represented by the following formula (6) or naphthalene represented by the following formula (7) The phosphonate is characterized in that it comprises the step of reacting the carbazole dialdehyde represented by the formula (5), Wittich or Wittich-Emons:

In this case, X = halogen, R = C1-C20 linear or branched alkyl group.

In the above-described production method, the two light emitting polymers are prepared using phosphonium salts or phosphonate monomers of naphthalene which are in relationship to each other.

In addition, the single layer electroluminescent device according to the present invention for achieving the above object of the present invention is characterized by using the light emitting polymer represented by the formula (1) or (2) as a light emitting layer.

In addition, the multilayer thin film electroluminescent device according to the present invention is characterized in that the light emitting polymer represented by Formula 1 or Formula 2 is used in at least one layer of the light emitting layer and the hole transporting layer.

Since the light emitting polymer according to the present invention has a structure in which naphthalene vinylene and carbazole vinylene units having high luminous efficiency and excellent hole transport characteristics are regularly repeated, an electroluminescent device manufactured using the light emitting polymer of the present invention Not only has excellent luminescence properties, but also facilitates injection of holes into the light emitting polymer and transport of injected holes. Therefore, when the light emitting polymer according to the present invention is used as a hole transporting layer in a multilayer thin film light emitting device including an electron transporting layer, a light emitting layer, a hole transporting layer and the like, holes are easily injected and transported, and are combined with electrons injected through the electron transporting layer. Since the formation probability of excitons is increased, the luminous efficiency of an electroluminescent element is greatly improved.

Hereinafter, preferred embodiments of the light emitting polymer according to the present invention, a manufacturing method thereof, and an electroluminescent device using the same will be described in detail with reference to the accompanying drawings. The following examples are given to further illustrate the present invention, and it will be apparent to those skilled in the art that the present invention is not intended to limit the scope of the present invention.

In a preferred embodiment of the present invention, as shown in Scheme 1 and Scheme 2, 1,4-naphthalene bis (triphenylphosphonium bromide) and 2,6-naphthalene, which are two monomers having a structural isomer relationship with each other By reacting bis (triphenylphosphonium bromide) with 9- (2-ethylhexyl) carbazole-3,6-dicarboaldehyde, respectively, poly [9- (2-ethylhexyl) -3, which is a light emitting polymer, 6-carbazolenevinylene-shift-1,4-naphthalenevinylene] [1,4-NAP-CAR] and poly [9- (2-ethylhexyl) -3,6-carbazolenevinylene-shift- 2,6-naphthylenevinylene] [2,6-NAP-CAR] is synthesized:

Example 1

[Preparation of poly [9- (2-ethylhexyl) -3,6-carbazolenevinylene-shift-1,4-naphthalenevinylene] [1,4-NAP-CAR]

0.34 g (10 mmol) of 9- (2-ethylhexyl) carbazole-3,6-dicarboaldehyde equivalent to 1 g (10 mmol) of the synthesized monomer 1,4-naphthalene bis (triphenylphosphonium bromide) After placing in a 50 mL flask, 5 mL of chloroform was added to dissolve both monomers. To this was added slowly using a syringe a solution of 0.59 g (50 mmol) of t-BuOK dissolved in 5 mL of ethanol. After reacting the reaction solution for 48 hours at room temperature, the mixture was extracted with methylene chloride and precipitated in methanol to obtain a polymer, and purified by Soxhlet extractor to prepare 0.32 g of pure polymer (yield: 32%). .

Example 2

[Production of Poly [9- (2-ethylhexyl) -3,6-carbazolenevinylene-shift-2,6-naphthylenevinylene] [2,6-NAP-CAR]

0.34 g (10 mmol) of 9- (2-ethylhexyl) carbazole-3,6-dicarboaldehyde equivalent to 1 g (10 mmol) of the synthesized monomer 2,6-naphthalene bis (triphenylphosphonium bromide) After placing in a 50 mL flask, 5 mL of chloroform was added to dissolve both monomers. To this was added slowly using a syringe a solution of 0.59 g (50 mmol) of t-BuOK dissolved in 5 mL of ethanol. The reaction solution was reacted for 48 hours at room temperature, extracted with methylene chloride and precipitated in methanol to obtain a polymer, purified by Soxhlet extractor to prepare 0.35g of pure polymer (yield: 35%).

As a result of measuring the solubility of the polymers prepared in Examples 1 and 2, it was confirmed that they are very well soluble in a general organic solvent, as measured by gel permeation chromatography (GPC), The mass average molecular weight was 5,000 to 25,000, and showed a dispersion degree of about 2.5.

As a result of thermogravimetric analysis (TGA), the prepared polymers showed a weight loss of less than 1% to a temperature of 350 ℃, it was confirmed that the thermally stable up to 350 ℃ or more.

UV absorption spectra for 1,4-NAP-CAR and 2,6-NAP-CAR, which are light emitting polymers prepared in Examples 1 and 2, are shown in FIG. 2. As can be seen in FIG. The UV absorption spectra of the prepared polymers 1,4-NAP-CAR and 2,6-NAP-CAR showed maximum absorption at 370 nm and 380 nm, respectively, and an absorption edge at about 500 nm and about 450 nm. Indicated.

3 shows PL emission spectra of 1,4-NAP-CAR and 2,6-NAP-CAR, the PL emission of 1,4-NAP-CAR and 2,6-NAP-CAR is 540. Maximum luminescence was shown at nm and 490 nm.

Meanwhile, two single layer electroluminescent devices were manufactured by using the polymers prepared in Examples 1 and 2 as light emitting layers and using ITO and Al as cathodes and anodes, respectively.

4 is an EL emission spectrum of the single layer light emitting device manufactured as described above, and the EL spectrum of the ITO / l, 4-NAP-CAR / Al and ITO / 2,6-NAP-CAR / Al light emitting devices is 560 nm and Maximum luminescence was shown at 490 nm, respectively.

In addition, as can be seen from the experimental results of FIGS. 5 and 6, the light emitting device manufactured according to the present invention showed typical diode characteristics in which current increased with an increase in applied voltage. Light can be emitted. At this time, the ITO / l, 4-NAP-CAR / Al device emitted orange light when viewed with the naked eye, and the ITO / 2,6-NAP-CAR / Al device emitted light close to white. Moreover, it was confirmed that the electroluminescent device manufactured according to the present invention operates stably without deterioration even at a voltage of 40 V or more.

As described and demonstrated in detail above, the light emitting polymer according to the present invention has excellent light emitting properties and hole transporting properties, is soluble in an organic solvent, as well as has good workability and workability, and according to the present invention, The light emitting polymer can be produced simply and economically.

In addition, the electroluminescent device according to the present invention not only has excellent light emission characteristics and hole transport characteristics, but also has an effect of operating stably without deterioration under high voltage.

Claims (6)

A light emitting polymer represented by Formula 1 below: [Formula 1] At this time, R = C1-C20 linear or branched alkyl group is represented, n> 4. A light emitting polymer represented by the formula (2): [Formula 2] At this time, R = C1-C20 linear or branched alkyl group is represented, n> 4. A phosphonium salt of naphthalene represented by the following formula (3) or a phosphonate salt of naphthalene represented by the following formula (4) includes a step of reacting a carbazole dialdehyde represented by the following formula (5) to a Wittich or a Vitihi-emons Method for producing a light emitting polymer represented by the formula (1) characterized in that: [Formula 3] [Formula 4] [Formula 5] [Formula 1] Wherein X = halogen, R = C 1 -C 20 linear or branched alkyl group, n> 4. A phosphonium salt of naphthalene represented by the following formula (6) or a phosphonate salt of naphthalene represented by the following formula (7) comprises a step of reacting a carbazole dialdehyde represented by the following formula (5) to a Wittich or a Vitihi-emons Method for producing a light emitting polymer represented by the formula (2) characterized in that: [Formula 6] [Formula 7] [Formula 5] [Formula 2] Wherein X = halogen, R = C 1 -C 20 linear or branched alkyl group, n> 4. A single layer electroluminescent device comprising the light emitting polymer according to claim 1 as a light emitting layer. The multilayer thin film electroluminescent device according to claim 1 or 2, wherein the light emitting polymer according to claim 1 is used in at least one of a light emitting layer and a hole transporting layer.